If I remember correctly, the last time this came up, they gave a good reason for not pardoning him. They knew that he was innocent, and that the government of the time had wronged him. Still, they refused to give a pardon. Not because they agreed with the actions against Turing, but because they felt that pardoning him would be an attempt to cover up their mistreatment of him.
They refused to pardon him, because it was their shame to know how wrongly they had acted, and they would not hide that shame.
They refused to pardon him, because it was their shame to know how wrongly they had acted, and they would not hide that shame.